Apparatus for charging, discharging, and turning the material in rotary-hearth furnaces



H. SPECKETER El AL March 5, 1935. 1,993,688 APPARATUS FOR CHARGING, DISCHARG'ING, AND TURNING THE MATERIAL IN ROTARY HEARTH FURNACES 15, 1931 '2' Sheets-Sheet 1 Filed July flemr/b/r Spec/fete) Lucia/ 9 Hebe/er Attorney ll fi f March 5, 1935. SPECKETER ET AL 1,993,683

AP F0 HARGING, DISCHARGING, AND TURNING PARATUS THE MATERIAL IN ROTARY HEARTH FURNACES Filed July 15, 1931 2 Sheets-Sheet 2 Patented Mar. 5, 1935 APPARATUS FOR CHARGING,

ING, AND TURNING THE MATERIAL IN DISCHARG- ROTARY-HEARTH FURNACES Heinrich Specketer,

Griesheim, and Ludwig Hebeler,

the-Main, Germany,

Frankfort-on-the-Mainort-onassignora to I. G. Farbenindustrle Aktiengesellschaft, Frankfort-onthe-Main, Germany Application July 15, 1931, Serial No. 550,846, In Germany August 29, 1930 6 Claim.

In the reverberatory furnaces employed, in-

metallurgy, for the continuous roasting of ores, and also for carrying out decomposition processes in the chemical industry, which are provided with hearths rotating in a horizontal plane (so-called puddling furnace with revolving hearth), it is desirable-in view of modifying the quantity treated and considering the differences in the velocity of the reactions of the charge, depending on its composition-that the rate of charging and discharging should be under control, within very wide limits, and .also that the possibility should be afforded of turning the charge material, as required, while the furnace is in operation. The means hitherto available for these purposes have been inadequate, especially in the case of processes which are conducted at relatively high temperatures, such as those in the vicinity of or above 1000 C. For such conditions it has already been proposed to provide a fixed, cooled stirring mechanism or, in the case of hearth furnaces.

with one or more stages, to employ a hollow central shaft and hollow rabbling or stirring arms, of cast metal, to accommodate the cooling medium. In both types it has been found that, when the members traversed by the'cooling water became leaky, the furnace has had to be shut down and the damaged parts removed. The resulting inconveniences are well known.

It has now been ascertained in accordance with the present invention that the means for controlling the charging conditions can be substantially simplified and improved by employing sep- 'arate conveyor devices, controlled independently of the furnace mechanism. According to the present invention, these devices are designed as cooling appliances, which side the furnace, in that they are pushed radially, from a point on the periphery of the furnace towards its centre, by means of a water-jacketed bearings, which rest on a travelling frame, adapted to travel a distance equal to the radial extent of thefurnace.

Conveyors of this type may be designed in a great variety of ways. In order to more clearly understand the nature of the invention; reference is made to the accompanying drawings which illustrate diagrammatically and by way of example, two particularly suitable embodiments of a device according to are actuated from.out-.

guide pipe or hollow shaft movably mounted in.

the present invention. the

details of which may, of course, be modified in many respects.

In the drawings Fig. 1 is a vertical section of part of a. furnace, showing the device in position therein, in elevation,

Fig. 2 is a similar view of another embodiment,

Fig. 3 is a plan view illustrating a combination of the devices shown in Figs. 1 and 2.

Figs. 4, 5 and 6 show a cross section of various parts of the conveyor device schematically illustrated in Figs. 1 and 3. Fig. '-7 is a detail in section of the cooling system.

In Fig. 1, an embodiment is illustrated which comprises, for the purpose of forming a coolable worm conveyor, a pipe a, of wedge-shaped cross section, which is disposed helically round a straight pipe or hollow shaft s, serving as an axle and is secured thereto, for example by welding; see also Figs. 3," 4 and 5. The front end (directed towards the interior of the furnace) of the pipe a opens at b (Fig. 4) into the pipe s, while the other end opens into the tubular fitting t shown in Fig. 5, which is connected with the rearwardly extending pipe or hollow shaft s of the worm, also shown in Fig. 5. The hollow shaft s is, at its rearward end, mounted in bearings 0 supported by the frame 1; and connected with means for actuating the worm, as shown in Figs. land 3. The rotary speed of the hollow shaft s and of. the worm secured thereto by welding can be varied, in accordance with the requirements of any given particular case, by means of a motor q and countershaft gear u. Inside the rearwardly extending hollow shaft s is situated, in a coaxial position, apipe d shown in Figs. 5 and 6, extending from the rearward end of the device, where it serves as inlet for the cooling water, up to the point w. The cooling water, after entering the pipe d and running through it, enters at 10 into the hollow shaft s; after flowing through this, 'it enters at that end of it situated in the middle of the furnace through the opening b (Fig. 4) into the wedge shaped hollow turns of the worm, through this it returns and enters at i into the tubular fitting t, as shown in Fig. 5; from there it flows through the openings e into the space between the hollow shaft s and the pipe d from which it escapes through the outlet 9. as shown in Figs. 5 and 6. 50

The worm-conveyor is adapted to be moved in and out of the furnace through a lateral opening hin the furnace masonry i, by means of a travelling frame a supported by, and secured to the pillars a: to the lower ends of which are mounted the wheels is adapted to travel along the rails z in a direction radial to the hearth of the furnace. The whole-device, being mounted upon and within the travelling frame, can, by the means described, be moved in a direction radial to the hearth as required. The advantage derived from this travelling device consists in the possibility of readily withdrawing the worm conveyor from the furnace, in case of defects, without cooling or even blowing out the furnace. If the circumstances necessitate the charged material being finally exposed to the maximumtemperature, the worm is set to convey it from a'charging point on the outside rim towards the central discharge outlet m.

The dimensions of the water-bearing turns a of the worm and their radial distance from the hollow shaft s are preferably such as to bring the lower edge of the shaft, during the operation, in a position above the level of the charged material, and the lower edge of the worm slightly above the floor of the hearth.

Moreover, the vertical position of the hollow shaft, and the worm secured thereto, can be regulated as required, by means of the 4 pillars :r of the frame 17, which are designed as screws that may be actuated by means of hand-wheels 3/, shown in Fig. 3, allowing the upper part of the frame a, the hollow shaft s and the worm secured thereto, to be raised and lowered, withreference to the hearth plate Z, as required. The worm conveyor is also suitable for processes conducted at temperatures up to over 1200 C. It should be noted that, even if the water cooling is abundant, the loss of heat through the worm is merely insignificant in comparison with the total heat consumption for operating the furnace, and more- 7 over, for example in cases of oxidizing decomposition, is more than counterbalanced by the increased efliciency resulting from the employment of the worm conveyor.

Fig. 2 depicts another embodiment of the cooled conveyor consisting of a water-cooled plough, introduced into the furnace, from outside, in the same manner as the worm. A concentrically jacketed pipe 12, traversed by the cooling water, is moved to and fro on a supporting frame 0, by means of a motor mechanism 11., shown in Fig. 3. The front end of p is closed by a plough 1', consisting for example of a wedge, divided internally by partitions for the water circulation and adapted to push the charge away from the floor of the hearth plate, by means of its knife edge. The plough can be made to operate all along the radius of the hearth plate, or only over a portion of same, according to requirements, or separate ploughs may be provided for the marginal and central portions of the plate, as shown in Figs. 2 and 3.

Moreover, by combining the worm conveyor and plough as shown in Fig. 3, a plough arrangement can be obtained in which the plough has no conveying action, and, if necessary, can be deprived of this capacity by designing it accordingly, when, for example, it is intendedsolely to turn the charge, or to lift such portions of the charge as lie directly on the fioor of the hearth plate and are unacted upon by the worm. More particularly is it important, in the case of charges with a tendency to incrust, that such tendency should be continuously counteracted by the cutting action of the plough. In conjunction with the plough, the worm also facilitates the treating of materials that tend to sinter, temporarily, in various spots in the case of fixed rabblers, such materials would be alternately piled up and pressed down by ti rabblers, whereby they would finally be fractured.

The combined action of worm and plough turns the charge over thoroughly and, by continually exposing new surfaces of the material in reaction intensifies the reaction, thereby enabling substantially thicker layers to be treated than is possible in the case of simple fixed (and, if necessary, cooled) rabblers, the result being both a substantially increased capacity and efficiency of the furnace.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

In the claims afilxed to this specification no selection of any particular modification of the invention is intended to the exclusion of other modifications thereof and the right to subsequently make claim to any modification not covered by these claims is expressly reserved.

We claim:-

1. A rotary hearth furnace comprising a rotating circular table having a discharge opening in the center thereof, movable hollow means extending radially into said furnace above said table, said hollow means being of a structure adapting it, when set in motion, to stir the material on said table and to move it toward said discharge opening, a liquid conduit connecting said hollow means to a source of cooling fluid outside said furnace, means exterior of said furnace for supporting said hollow means, means exterior of said furnace for imparting motion to said hollow means, and means exterior of said furnace for adjusting the radial length of said hollow means in said furnace.

2. A rotary hearth furnace comprising a rotatable circular table having a periphery substantially circular in shape, a radially disposed charging, discharging and stirring worm conveyor mounted above the upper surface of said circular table, a conduit connecting the interior of said conveyor with a. source of cooling liquid outside said furnace, means outside the furnace for adjusting the radial length of the worm conveyor in said furnace, driving means outside the furnace whereby said conveyor may be operated at variable speeds, and means for raising and lowering said conveyor relatively to the said circular table.

3. A rotary hearth furnace comprising a rotatable circular table, a frame mounted outside the furnace and radially disposed above said table, a radially disposed rotatable pipe mounted on said frame, a hollow worm secured to the outside of said pipe and having one of its extremities in communication with the interior of said pipe, means for raising and lowering the upper part of said frame, together with said rotatable pipe and the worm secured thereto, relatively to said rotatable table, a conduit connecting the interior of said pipe and worm with a source of cooling liquid outside said furnace, means outside the furnace for moving the frame radially with respect to the table and means outside the furnace for rotating the pipe at variable speeds.

4. A rotary hearth furnace comprising a rotatable circular table, having a discharge opening in the center thereof, rotatable hollow means extending radially into said furnace above said table for stirring the material fed to said table and for moving it towards said discharge opening, a conduit connecting the interior of said hollow means with a source of cooling liquid outside said furnace, means for supporting said hollow means exteriorly of said furnace, means for rotating said hollow means within the hearth furnace, means for moving said hollow means radially to the hearth furnace and means for raising and lowering said hollow means relatively to the circular table.

5. A rotary hearth furnace, comprising a rotatable circular table, having a discharge opening at the center thereof, a stirring, charging and discharging device for said table comprising a movable hollow arm projecting radially into said furnace above said table and having means thereon for stirring and advancing the material fed to said table towards said discharge opening upon motion of said hollow arm, a conduit connecting the interior of said arm and the means thereon with a source of cooling liquid outside said furnace, means for mountingsaidarm exteriorly of said furnace, means for radially moving said am with respect to said furnace, means for imparting motion to said arm, and means for raising and lowering it relatively to the rotatable circular table.

6. A rotary hearth furnace, comprising a rotatable circular table, havinga discharge opening in the center thereof, a hollow shaft extending radially into said furnace above said table, a hollow worm encompassing said hollow shaft and secured to it, and with one end thereof in communication with that end of said hollow shaft extending near to the center of the hearth, a hollow fitting encircling said hollow shaft at a point between the ends thereof, the other end of said worm being secured to said hollow fitting and in communication therewith, a pipe concentrically arranged within said hollow shaft having its outer circumference spaced from the inner circumference of said hollow shaft and extending therein up to a point intermediate the ends of said fitting, a liquid tight partition connecting the outer circumference of the inner end of said last mentioned pipe with the inner circumference of said hollow shaft and a conduit connecting said fitting to said hollow shaft at a point behind said partition whereby .a cooling fluid admitted through said last mentioned pipe will pass through said hollow shaft through said worm and through said fitting to the exterior of the-furnace in sequence, means for supporting the hollow shaft exteriorly of said furnace, means for radially means for rotating it and means for raising and lowering it relatively to the said hearth.

HEINRICH SPECKETER. LUDWIG HEBELER.

moving the hollow shaft within said furnace, 

